vignette

Make or reverse a natural vignetting effect.

The filter accepts the following options:

angle, a

Set lens angle expression as a number of radians.

The value is clipped in the [0,PI/2] range.

Default value: "PI/5"

x0

y0

Set center coordinates expressions. Respectively "w/2" and "h/2" by default.

mode

Set forward/backward mode.

Available modes are:

‘forward’

The larger the distance from the central point, the darker the image becomes.

‘backward’

The larger the distance from the central point, the brighter the image becomes. This can be used to reverse a vignette effect, though there is no automatic detection to extract the lens angle and other settings (yet). It can also be used to create a burning effect.

Default value is ‘forward’.

eval

Set evaluation mode for the expressions (angle, x0, y0).

It accepts the following values:

‘init’

Evaluate expressions only once during the filter initialization.

‘frame’

Evaluate expressions for each incoming frame. This is way slower than the ‘init’ mode since it requires all the scalers to be re-computed, but it allows advanced dynamic expressions.

Default value is ‘init’.

dither

Set dithering to reduce the circular banding effects. Default is 1 (enabled).

aspect

Set vignette aspect. This setting allows one to adjust the shape of the vignette. Setting this value to the SAR of the input will make a rectangular vignetting following the dimensions of the video.

Default is 1/1.